If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.

Nitecore i2 and i4 Chargers - 2014 Edition - Review

REVIEWER'S NOTE: I see HKJ has already provided more detailed circuit testing of these two models. I recommend readers check out his excellent i2 2014 and i4 2014 reviews for more detailed info.

This is a review of the newly revised for 2014 editions of the Nitecore Intellicharger i2 and i4. Please see my earlier review of the previous i4 V2 from 2012.

Note the big "2014 VERSION" in red on the boxes above.

Has much changed from the previous version? For that, let's see how the results compare to my earlier i4 V2 review.

The i4 generated a lot of interest when it first came out, given its stated ability to "intelligently" handle both Li-ions and standard NiMH/NiCd rechargeable batteries. It does this by detecting the voltage of the cells when you insert them, and then applies the appropriate charge algorithm.

As always, I freely admit that I am not as well versed in electronics or circuitry as some of the other members here. So I suggest you consult with the true experts in this forum if you want to know more than just the basic current/voltage runtime relationships that I can measure here. Speaking of which, I am following HKJ's excellent Measurement on Flashlight methods for the current/voltage testing.

Note the above is what the manufacturer reports for the chargers  scroll down to see my actual review findings.

I4 2014

I2 2014

My samples both came with a standard 110 AC power adapter designed to North American plugs. The units support 100  240V AC, 50/60Hz, so those outside of North America can use it fine (with the appropriate terminal plug). A 12V DC car adapter is available separately.

A key point to specs above is that while the i2 has two independent channels (for 500mA), the i4 also only has two channels (but for up to 750mA). Since the i4 actually has four wells, that means that current needs to be shared between two wells. While the charger label reports this as "0.375A*4", in actual fact the charger remains at 750mA for each bay  but it alternates charging by cycling off/on about once every second for each battery. This effectively results in the same thing, but the cell is actually being charged at 750mA for a 1sec on, 1sec off, cycle.

Unfortunately, Nitecore still does not identify which of the four wells are paired in this fashion on the i4. As before, I determined from my testing that the paired wells are #1 & #3 and #2 & #4 (i.e., paired wells are separated by an independent well in between).

As before, the cabling and overall build of the units seem good (i.e., good length on the cables, solid base unit).

The most obvious visual difference for the new 2014 models is the presence of the metal rail for the battery slider. Previously, these were just spring-mounted (and often poorly lubed). As a result, I find the spring action a lot smoother on these new 2014 models.

The units can accommodate a range of cells, although wide cells (i.e., 26650) will need to go into the outside wells of the i4 to make proper contact. Note that the overall size of the chargers hasn't changed, so you will find it a bit tight to get some really long protected cells in there. Personally, I would have liked to have seen them extend the units by a mm or two.

To give you an idea what the units look like with cells installed:

Note: I didn't have the unit plugged in for these shots, which is why you don't see any of the indicator lights lit up.

There are three yellow lights located over each charging bay, and a blue power indicator at the top right hand side of the unit (lights up when AC/DC power is supplied).

When you insert a battery into the charger, the three yellow lights over the bay indicate the charging status by the number of flashing LEDs (counting from the bottom up). Three solid LEDs means the battery is fully charged and the unit has stopped charging (in theory  scroll down for a discussion on NiMH).

Here is a quick video overview of the physical builds of the chargers:

Voltage/Current Measurements

To examine the performance of the chargers, I have directly monitored charging current and voltage with a data-logging DMM - but on separate runs. While plotted together, these means the voltage and current traces may not exactly correspond in time.

For these tests, I have used my standard AW protected 18650 (2200mAh) and Sanyo Eneloop AA NiMH (2000mAh). The cells used here have all had a good number of cycles on them, but are still in reasonable condition. Drained batteries (typically resting voltage typically ~3.0-3.2V) are used for these tests.

The i4 2014 shows a good simulated constant-current/constant-voltage (CC/CV) algorithm, as before. The specific voltage run above had a few restarts during the constant current (CC) phase, and took a bit longer on the constant voltage (CV) phase, so I would go with the current run as the best indicator of typical performance (on 2200mAh cells).

As you can see above, the i4 2014 terminated at 28mA with a resting voltage of ~4.21V. This is very similar to my original i4 V2 review. The termination current is a bit lower now, and the resting voltage a bit higher (resulting in slightly longer charging time). But that could just be variability between charger samples.

The i2 2014 similarly has a good CC/CV charging algorithm. While the charging current is not as high as the i4 2014 in the CC phase, it doesn't seem to drop off as rapidly in the CV phase (although that could be a bit of battery variability). Again, the current run above seems the most representative of what you can expect for this unit (i.e., it takes longer to fully charge an 18650 than the i4). Termination level is again good.

FYI, the "dips" in the graphs above have to do with how the chargers operate  they actually pause charging once every two seconds (presumably to check the battery voltage). Not sure why they both do this, but it's been a common feature of these models from the beginning. My sampling rate is once every 30 secs above, hence the why you don't see a continuous "wall of noise", but just sporadic dips (i.e., on the odd times when the sampling took place during a charging pause).

I haven't bother showing what the paired charging would like, or RCR cells, but you can see my earlier i4 V2 review for that. Effectively, it may take up to twice as long to charge cells in paired channel bays.

So how does NiMH look?

The chargers run at their max CC cycle initially. I am not sure of the termination method being used, but it looks like it could simply be based on cell voltage. The recommended termination method for NiMH is dV/dT, which is based on a characteristic increase in the positive slope of voltage versus time. As before, this does not seem to be the case here.

Again, due to the lower charging current per channel, the i2 will take longer than the i4 to charge NiMH batteries.

But there is something different about the new 2014 versions and NiMH charging  when the charger "terminates", it actually drops to a ~110mA continuous "trickle charge". This appears to be the way the charger makes up for the voltage-based termination method (which may leave the batteries somewhat undercharged), by providing a prolonged lower-level "trickle charge".

Nitecore informs that that the "trickle charge" is normal to maintain the charge status of the NiMH batteries, and won't harm the cells. But it would NOT be a good idea to leave these cells in there too long after the charging status indicates they are done. I would recommend you pull the cells within an hour so of the "termination" notice.

The full charge capacity seems to be good on both chargers, if you give them that extra hour or so of "trickle charge". My Maha C9000 charger reports a typical discharge capacity to these cells (upon subsequent discharge), comparable to my Maha's own charge cycle performance.

FYI, you can safely charge NiMH and Li-ions at the same time, even in paired bays.

As with all chargers, your cells will slowly drain if left in the unit without power. I measured the at-rest drain (when not connected to AC power) on the i2 2014 as 1.4mA for Li-ion, and 0.06mA for NiMH. For the i4 2014, I measured 0.77mA on Li-ion, and 0.15mA on NiMH.

One last comment  these new units seem to take a little longer to actually start charging than the previous models. While the indicator lights come on as quickly as before, I measured a lower initial current of ~125mA for about 10-20 secs or on each model, on all batteries, before jumping up to the max rated current. Note sure why this is, but it is another sign of a circuit change from the earlier versions.

Preliminary Discussion

The Nitecore Intellicharger line has been popular here since their initial release  likely due to their dual support of both Li-ions and NiMH batteries. Physically, I can only see the improved battery rail in each well, but I can infer internal circuit changes as well. The new rail is definitely an improvement over the older springs  I found the slide action noticeably smoother now.

On Li-ions, overall performance seems similar to the early versions, with a good CC/CV-like algorithm (and with a nice and low charging rate at termination).

NiMH charges with a consistent constant max current, but seems to use a simple voltage measure for the termination signal (as opposed to the recommended dV/dt). One thing that is new for the 2014 models is that Nitecore has added a ~110mA "trickle charge" to the NiMH algorithm, to help ensure that the cells wind up being fully charged. This is necessary due to the simple termination method used (which may under-estimate charge status). Unfortunately, this means that the batteries are still charging after the indicator lights indicate charging is over  which is not something I like to see.

It is hard to say how long you should let the charger continue charging the NiMH cells beyond the indicator "termination"  but I recommend you pull them within an hour or so. Certainly, you wouldn't want to leave them in there over days, as this may wear them down eventually. Better to have slightly undercharged cells than overcooked ones!

In terms of choosing between the two models, it largely comes down to what your needs are. The i4 has a larger max charging current, leading to shorter charging times. However, the i2 would be more suitable for lower capacity cells (e.g., RCR, 14500, and AAA), due to the slightly lower charging current. Effectively, both units can only fully charge two wells at a time (i.e., the i4 has to alternate the current between paired wells).

Physically, there is a little more space to accommodate wider batteries in the i2 (e.g. 26650)  but the i4 is still serviceable in this regard, if you use the outside wells. Both models are still tight for length with protected cells - I would prefer to see Nitecore add an extra mm or two to well height on both models.

At the end of the day, these are incremental upgrades to the Intellicharger line from Nitecore. I think these chargers still offer good value for the money - especially compared to discount "budget" chargers that cost almost as much, but with unknown charging algorithms. They are also particularly useful for less sophisticated users who are just starting to use Li-ions (and may thus inadvertently try to charge NiMH and Li-ion on the same device - a real no-no on just about every other charger!).

But there are certainly better dedicated NiMH chargers out there. And the Li-ion charger market has expanded a lot in recent years too. There are now more sophisticated chargers that cost more but offer significant additional features (e.g., the option to set the max charge current, or read out battery voltage during charging). If you need a dedicated Li-ion-only charger, you may want to consider investing a bit more for an expanded feature set. But if you want combined Li-ion/NiMH support (and at a reasonable price), the i4 and i2 seem to continue to fit the bill.

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

What is the Eneloop Pro cell in the photo of the I4? When I gogle it all I find is what seems to be a high current version of the XX AA LSD cell, which this is definitely not.

Originally Posted by HKJ

It is the same as eneloopXX.

Yes - although more specifically, they are the new packaging for the 2nd generation Eneloop XX.

The original AA-version Sanyo Eneloop XX released in 2011 was 2500mAh nominal (2400mAh minimum), but had reduced long-term discharge rates compared to the original Sanyo Eneloop (i.e., only 75% capacity at one year for the 1st gen XX, compared to 90% for the regular Eneloop).

The second generation XX came out in Jan 2013, with a raised capacity of 50mAh (i.e., 2550 nominal, 2450mAh min), and improved discharge rate (although I don't know the exact number).

After Panasonic acquired Sanyo, these became renamed the Panasonic Eneloop Pro. The rated specs are the same as the 2nd gen XX, although I do see the self-discharge rate is now reported as 90% capacity at one year (i.e., back up to the original eneloop standard). Product code is BK-3HCCA for the Panasonic Eneloop Pro AA cells.

I've started adding these to my reviews, given the LSD characteristics are back up to original eneloop standards (and I am finding it hard to source the 4th gen Eneloops locally now).

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

I haven't been able to find out why my (~1 year old) i2 will charge AAA Nimh batteries directly from a 15 watt solar panel but not Li-ions. Just thought I would bring it up in case anyone has a simple work around that would allow direct charging a single 18650 from a Goal Zero 15w panel. (Or an explanation why it won't work) Thanks

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

I have the Nitecore i2 charger and use a Nitecore 14500 750mAh battery in my Sunwayman V11R. I use the flashlight maybe 10min or less during the week at a medium-high light output. I've measured weekly discharge from full 4.21vdc to 4.02vdc by the end of the week. This is a small voltage drop of only .2vdc.

How often should I be charging this battery to obtain optimum performance and number of cycles? At what voltage should I recharge?

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

I'm happy to let any of the charging experts here weigh in ...

But in general terms, I think the main advice is that it won't hurt to charge frequently. The two major charging issues with Li-ions are over-charging (i.e. >4.2V) and over-discharging (i.e. <2.7V) - both of which can damage a cell, and neither are likely an issue here. Other issues are the charging and discharging rate. At 500mA, the i2 is not ideal for charging low-capacity cells like 14500, but it is perfectly acceptable (and better than many). A trick HKJ has noticed is to pop a NiMH battery in the other well - this helps "fool" the charger into a lower effective charge rate. As for discharge rates, the V11R won't be too hard on the ICR cell you are using. Long-term, Li-ions do better if they are stored at lower charge levels than Hi - but if you are frequently using the light, you are probably still better off keeping it relatively "topped off" in case you need the runtime.

Short version - you are fine to keep topping up every week, as you are doing.

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

LiIon batteries has a shorter lifetime while fully charged, especially if it is hot. That is the reason they usual are delivered only half charged.

Fully agreed. The question is what do with a light you are using every day. Personally, I like to keep my EDC fairly well topped up (in case I need the extended runtime while I'm out). But that said, there is no reason why you need to fully top them up to ~4.2V - you can always pull them out of the charger before they are fully charged.

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

ive read a lot that you need to be very careful not to leave batteries on the charger for too long or you risk a fire/explosion is this charger safe to leave batteries on for longer than required to fully charge?
IE over night, I usually will put a battery on the charger over night and take it off in the morning of after I get back from classes if I forget. Is the nitecore charger able to detect that the battery is indeed fully charged and stop charging it or will it continue to charge even when its full?
in other words is it safe to just stick a battery on the charger and leave it over night instead of checking it every 15 or so minutes to make see if the battery has finished charging?

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

Originally Posted by pokelda2

Is the nitecore charger able to detect that the battery is indeed fully charged and stop charging it or will it continue to charge even when its full?

Like any good quality Li-ion charger, the Nitecore i2 and i4 terminate the charge once the battery is full. I recommend people only use chargers like these that terminate (i.e., true "trickle chargers" would be damaging for Li-ions).

However, that doesn't mean you should leave the charger unattended. Any protection system can fail, so it is good practice to only charge cells when you are around, and pull them once you see they are terminated. This is again why I don't like the behavior on NiMH on these new models, where you are supposed to leave them on the charger for a period of time after the indicator suggests they are done.

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

Originally Posted by selfbuilt

That right - the 3.2V nominal LiFePO4 cells required different chargers, due to the lower max cell voltage.

I'm currently shopping for a charger for batteries for my SureFire E2D LED, eneloop batteries, and for vape batteries and noticed the next model up of this brand of chargers does LiFePO4 batteries. The only downside is you have to manually select the voltage for them, while every other type of battery it charges will auto-select/detect. I definitely like the digital display so you can see what it's doing.

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

Originally Posted by Andrew LB

I'm currently shopping for a charger for batteries for my SureFire E2D LED, eneloop batteries, and for vape batteries and noticed the next model up of this brand of chargers does LiFePO4 batteries. The only downside is you have to manually select the voltage for them, while every other type of battery it charges will auto-select/detect. I definitely like the digital display so you can see what it's doing.

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

Help.

I too need a charger and 2, 18650 batt.s for my PD35. Orbtronic in Florida had a good Xtar and 3400 combo but, lately they have been out of stock on almost everything. I don't know what happened there so I emailed them to ask. If I hear back I'll post. Failing that option what is recommened now and where do I get it too? Thanks!

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

Thankyou Selfbuilt, and HJK for your reviews.

I bought the i4 2014 version a few months back, and used it without paying too much attention. I just realized that it took about 6 hours to charge 4 fully depleted Duracell Iron Core 2400ma batteries. Looking at this review, I guess that is about right.

Is this a particularly slow charger? And if so, I guess that is better for the life of the batteries?

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

Originally Posted by Poppy

Thankyou Selfbuilt, and HJK for your reviews.

I bought the i4 2014 version a few months back, and used it without paying too much attention. I just realized that it took about 6 hours to charge 4 fully depleted Duracell Iron Core 2400ma batteries. Looking at this review, I guess that is about right.

Is this a particularly slow charger? And if so, I guess that is better for the life of the batteries?

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

Originally Posted by Poppy

Is this a particularly slow charger? And if so, I guess that is better for the life of the batteries?

I've seen slower, I've see faster. I'd have to leave it the NiMH charging experts here, but I think a little faster would be good. As Patt points out, charging will be twice as fast if you only do two cells at time (in non-paired wells). Of course, if you need to charge 4 cells, it's going to take the same amount of time in total.

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

Originally Posted by selfbuilt

I've seen slower, I've see faster. I'd have to leave it the NiMH charging experts here, but I think a little faster would be good. As Patt points out, charging will be twice as fast if you only do two cells at time (in non-paired wells). Of course, if you need to charge 4 cells, it's going to take the same amount of time in total.

selfbuilt,
Thanks for the response.

I bought this charger because it doesn't require charging in pairs, and does monitor batteries individually, AND the other NiMH chargers I have, do charge in pairs. My RadioShack Enercell charger claims 1.5V/1.0A per slot AA, and 1.5V/0.4A per slot for AAA. It claims to be a 1-2 hour charger. I never paid attention to it, I only used it a couple of times.

But in a power outage where I am lending and charging batteries for my family and neighbors... this would be too slow, and I'll need to press the other units into use too.

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

REVIEWER'S NOTE: I see HKJ has already provided more detailed circuit testing of these two models. I recommend readers check out his excellent i2 2014 and i4 2014 reviews for more detailed info.

The most obvious visual difference for the new 2014 models is the presence of the metal rail for the battery slider. Previously, these were just spring-mounted (and often poorly lubed). As a result, I find the spring action a lot smoother on these new 2014 models.

The units can accommodate a range of cells, although wide cells (i.e., 26650) will need to go into the outside wells of the i4 to make proper contact. Note that the overall size of the chargers hasn't changed, so you will find it a bit tight to get some really long protected cells in there. Personally, I would have liked to have seen them extend the units by a mm or two.

To give you an idea what the units look like with cells installed:

.

I agree with selfbuilt, and I think that HKJ also commented that he would like to see the battery compartment a little longer. Personally I would like to see the metal tab longer also. I have to insert my fingernail between it and the battery to extract the battery.

I placed a ribbon across the bays, and taped one end in place (taped it to the back of the unit and wrapped it around to the front) to aid in the extraction of batteries. I am sure that you have seen toys or other items that take a multiple of batteries and a ribbon is inserted so that they are easily removed.

Re: Nitecore i2 and i4 Chargers - 2014 Edition - Review

Originally Posted by Poppy

or other items that take a multiple of batteries and a ribbon is inserted so that they are easily removed.

i use diy ribbons made out of 3M Scotch tape to remove Eneloops from all kinds of battery holders.
since the i4 has sliders, imho it doesn't need ribbons. one can just push the battery more, get the sliders to move, and then lift the battery out of the tray with your fingers.